Cyclically operable printing and proportional spacing apparatus



1969 R. H. LEE 3,420,164

CYCLICALLY OPERABLE PRINTING AND PROPORTIONAL SPACING APPARATUS Filed Dec. 20, 1965 so 0 I 1 12 s 40 l L L 45 54 23 56 37 coubgaa COUNTIER COMPARATOR PCOMPARATOR COMPUTER n E in - F|G.2. FIGS. 1% \5 Roman: HENTYVEBEEOR BY Mu (m5 ATTORNEY United States Patent Ofiice 3,420,164 Patented Jan. 7, 1969 52,176/64 US. Cl. 101 93 1m. (31.12413 5 Claims ABSTRACT OF THE DISCLOSURE An on-the-fly printer is described in which type barrel is formed to represent a number of typewheels, each carrying a complete type font and is mounted on a shaft for .rotation opposite a row of print hammers. A paper web is fed between the print hammers and the type barrel and a line of characters is printed on the paper by impelling the hammers towards the type barrel as characters required in the various positions in the printed line pass the printing position. The paper web is fed line-by-line through the printer by tractor drives which include tractor bands engaged with marginal perforations in the paper web and also include a cam arrangement for shifting the web sideways by a fraction of the inter-typewheel spacing.

Printing of a single line of characters takes place in a series of cycles and the cam is operated to produce this sideways paper shift between these printing cycles. Thus, by selecting certain characters to be printed in each of the print cycles the effect of the sideways shifting operation is to alter the normal inter-character spacing to achieve proportional spacing of the characters recorded in the printed line.

The printing arrangement may be coupled, for example to a computer, and includes an indicator associated with the camming arrangement to show the extent of the sideways shift applied during its cur-rent printing cycle. A character store is provided to store a complete line of characters to be printed. A control arrangement then allocates the characters from the store to each of a series of printing cycles and initiates printing of those characters during the appropriate cycles.

This invention relates to cyclically operable printing apparatus.

In one form of known cyclically operable printing apparatus, in which a line of characters is printed in each printing cycle, the type characters are carried on a cylindrical type barrel. A separate font of type characters is provided for printing in each columnar position of the record medium, and each font is arranged in a separate row extending around the periphery of the barrel. Separate print hammers are provided to co-operate with each peripheral row of characters respectively, the hammers being arranged in a line parallel to the central axis of the barrel. The record medium on which printing is to be effected is feed line by line between the type barrel and the hammers and an inking ribbon is fed between the record medium and the type barrel. Rotation of the barrel about its axis causes each type character of the fonts to be brought in turn into an operative position facing the hammers. Thus by operating the print hammer associated with a columnar position in which printing is desired at a time when the character required to be printed is in the operative position, printing of that character is effected.

It will be seen, therefore, that the centre to centre spacing of the printed characters in a line on the document is the same as the centre to centre spacing of the peripheral rows of type characters on the type barrel and is invariable. However, the appearance of a printed document is enhanced if the characters in a line are proportionally spaced, i.e., the centre to centre spacing of adjacent characters is varied in dependence on the width of the characters. In addition, when the lines of characters are to be justified, the spaces between words and possibly the spacing of individual characters in the lines must be adjusted such that the total length of each line is uniform. With known cyclically operable printing apparatus the characters can only occupy positions on the document corresponding to the columnar printing positions of the printer and consequently the spaces between words can be varied.

only in multiples of the spacing of the columnar printing positions.

Furthermore, in known apparatus it has been necessary to provide a font of type characters and a co-operating hammer mechanism for each position in which it is desired to print in the line on a document.

It is an object of the invention to provide improved cyclically operable apparatus capable of printing characters at centre to centre spacings which are less than the spacing of adjacent fonts of characters and in which if desired the spacing may be varied.

According to the invention apparatus for printing a line of characters on a record medium includes printing means in which all type characters of a font are made available for printing at a plurality of columnar printing positions in each of a succession of printing cycles; means to store a line of characters to be printed; means to cause relative displacement, in a direction aligned with the line of characters to be printed, between the record medium and the columnar printing positions by a fraction of the spacing of the columnar printing positions for each printing cycles; means to allocate to each stored character of the line one of the columnar printing positions and one of the printing cycles; and means to read out signals representing the stored characters to effect printing of the characters in the printing cycles allocated to the respective characters whereby at least some of the characters in the line are printed on the record medium with a centre to centre distance less than the spacing of the columnar printing positions.

Printing apparatus operating in accordance with the invention will now be described in more detail, by way of example, with reference to the accompanying drawings in which:

FIGURE 1 shows diagrammatically printing apparatus constructed to permit variable spacing between adjacent printed characters.

FIGURE 2 shows a tractor paper feeding mechanism for the apparatus shown in FIGURE 1,

FIGURE 3 shows a section through part of the tractor mechanism of FIGURE 2, and

FIGURES 4a through 4; show a word printed without a relative paper displacement and the progressive printing of the same word with such displacement.

The printing apparatus consists of a cylindrical type barrel 1 carrying a plurality of fonts of type characters 2. Each font of characters includes one of each kind of char acter which it is desired to print, a font of characters extending in a separate row around the periphery of the type barrel 1 and like characters in each font lbeing arranged in line along the length of the barrel. A plurality of hammers 3, one for each font, of which for the sake of clarity only four are shown in FIGURE 1, are arranged in a line parallel with the axis of the type barrel. Each hammer 3 has associated with it an operating mechanism 4. A record medium 5, which consists of a web of paper, 011 which printing is to be effected is fed between the type barrel 1 and the hammers 3 by means of two pairs of tractor feeding mechanisms. The tractors 6 have pins which engage in perforations in the edges of the web 5, one pair of tractors being arranged to engage the left hand edge of the web and the other pair of tractors (not visible in FIGURE 1) being arranged to engage the right hand edge of the web. An inking ribbon (not shown) is fed between the web and the type barrel 1. The type barrel 1 is supported, for rotation about its axis, by a shaft 7 which is driven by an electric motor 8. Rotation of the type barrel about its axis causes the characters 2 in each font on the barrel to be brought successively into positions for printing in which they are facing and aligned with the hammers 3. Operation of the hammer 3 corresponding to a selected columnar printing causes the paper web and inking ribbon to be pressed together momentarily between the type character and the operated hammer thereby effecting printing of that character.

The two upper tractor feeding mechanisms 6 are supported on parallel splined shafts 9, 10 and the two lower tractor feeding mechanisms 6 are similarly supported on parallel splined shafts 11, 12. The upper and lower tractor feeding mechanisms are driven by rotation of the shafts 10 and 12 respectively. The tractor mechanisms may be adjusted laterally by sliding them along the shafts so as to accommodate different widths of paper web and so as to position the web in a desired lateral position relative to the type barrel. The initial lateral positioning of the entire tractor mechanisms may be effected by lead screws (not shown). In order to permit printing of characters at spacings on the paper which are different from the spacing of the fonts of characters on the barrel 1, the tractors are displaced laterally by an incremental displacement between each printing cycle.

Referring to FIGURE 3 which shows a section of part of one of the lower tractor mechanisms, each complete tractor mechanism is formed in two parts movable transversely relative to one another. One part consists of a slide member 13 which slides along shaft 11 (shaft 9 for the upper tractors) and the other part consists of a casing 14 which slides on the member 13. The casing 14 contains pin wheels 15 which carry a tractor band 16. Displacement of the casing, and thus the pin wheels, relative to the slide member 13 is effected by a stepped cam 17 in the slide member 13 acting on a pin 18 attached to the casing 14. A spring 19 is provided to return the casing against the cam. The cam 17 is rotatable by splined shaft 11. The shaft 11 is driven from the shaft 7 by suitable reduction gearing, illustrated in FIGURE 3 by pulleys 20, 21 and belt 22, but which may consist of a train of gear wheels. The upper tractor mechanisms are of similar construction and the shaft 9 is driven in synchronism with shaft 11 so that all four of the tractor mechanisms are displaced in steps transversely in synchronism. The ratio of diameters of the pulleys 20 and 21 is selected so that the shaft 11, and therefore the cam 17, makes one revolution while the type barrel makes a plurality of complete revolutions. As shown in FIGURE 3, the cam 17 has five steps. Because the cam 17 is shown in section only three steps are visible, corresponding to the first, third and fifth levels of displacement, and it will be understood that the other half of the cam 17 (not shown) will provide steps corresponding to the second and fourth levels of displacement. Interleaving the displacement levels in this way ensures that during one complete revolution of the cam 17 the lateral displacement for any step cannot exceed two increments of movement. In the case shown, where five steps are provided, the ratio of the speeds of rotation of shafts 7 and 11 may be 5:1. In this case, the type characters on the barrel 1 may be arranged so that there is a gap between the last and first characters of the fonts and the cam 17 is then arranged to step the tractor mechanisms during the time interval that the gap is at the printing position. Alternatively, if, as is the case shown in FIGURE 1 there is no gap between the last and first characters, the type barrel executes an idle revolution while the stepping takes place. In this case, using a five step earn as shown in FIGURE 3, the ratio of speeds of the shafts 7 and 11 is 10:1. A complete printing cycle then includes an operating and an idle revolution of the barrel 1 and for successive printing cycles the paper web is displaced in steps transversely.

During the operative revolution of a printing cycle the type barrel completes one revolution all the characters of the fonts are made available for effecting printing at their respective columnar printing positions. Thus during one printing cycle desired characters may be printed at every columnar printing position, the hammers being operated as each line of characters comes into the printing position to effect printing at all those columnar printing positions in which the available character is required to be printed.

Since the type barrel rotates continuously, selection of a character to be printed is accomplished by timing the operation of the hammer relative to the revolution of the type barrel.

A plurality of identical hammer control circuits 23, of which one is shown in detail as comprising a store 24, two comparators 25, 26, and an AND gate 27, are provided for controlling the operation of the hammers 3. The store 24 provides a number of stages 38 for storing code element signals representing a character to be printed and further stages 39 for storing information relating to the printing cycle in which the character is to be printed.

A slotted disc 28 is mounted on the shaft 7 so as to rotate in synchronism with the type barrel 1. The disc 28 has a plurality of slots corresponding to the different type characters 2 of the fonts such that when a line of type characters is in the printing position, the corresponding slot in the disc 28 lies between a light source 29 and a photocell 30. Thus, as each line of characters comes into printing position, the photocell 30 generates a signal which is passed to a counter 31. One of the slots in the disc 28 is deeper so that once in each revolution of the type barrel a light source 32 causes a photocell 33 to generate a signal which is utilised to reset the counter 31 to zero. The count in the counter at any instant therefore corresponds to the particular character which is available for printing at that time. A comparator 25 receives the count in the counter 31 and also receives signals from the stages 38 of the store 24. When the count corresponds to the stored character, the comparator 31 generates an output signal which is applied to one input of an AND gate 27.

The shaft 11 which drives the stepped cam 17 also carries a slotted disc 34. This disc has a number of relatively shallow slots 44 corresponding to the steps of the cam 17. When a slot 44 of the disc 34 lies between a light source 35 and a photocell 36, a signal is passed to a counter 37. Reset signals are generated once in each revolution of the shaft 11 by means of one relatively deep slot 45 in the disc and a photocell 40 and light source 41. The count in the counter 37 indicates the angular position of the cam 17 and therefore also indicates which printing cycle is occurring. The count of counter 37 and the contents of the storage 39 are applied to the comparator 26. When these inputs correspond to one another, the comparator 26 applies a signal to the other input of AND gate 27.

When both inputs of AND gate 27 are energised by comparators 25 and 26, the gate 27 generates a signal which operates the hammer circuit 4 thereby printing that character which is represented in the store 24.

It will be seen that during the operative revolution of the type barrel in one printing cycle, all those characters which are stored in the stores 24 of control circuits 23 and which are allocated to this particular printing cycle will be printed in a line on the paper web. During the time interval between the last and first characters being available for printing in successive cycles, the paper web is displaced transversely by the cams 17 acting on the tractor feeding mechanisms. In the following printing cycle, all those characters in the stores 24 and which are allocated to this following printing cycle will be printed in the same line on the paper Web. After five printing cycles, printing of a line is complete and the paper web is returned to its initial transverse position and the tractors also effect feeding of the paper by one line reading for the next line of printing. FIGURES 4a through 4 show, on an enlarged scale for the sake of clarity, the result of the transverse displacement of the paper web during a succession of printing cycles. FIGURE 4a shows the arrangement of characters in printing the word accommodation as they would appear if printed from a row of equally-spaced type fonts. Thus, this figure shows the relative spacings between the characters which would result from the printing of the entire word in a single cycle Without any transverse displacement of the paper web. FIGURES 4b through 4 show the progressive printing of the same word in five printing cycles with a transverse displacement of the paper web relative to the type fonts. In each case the displacement is in a direction such that characters to be recorded during the following cycle are displaced towards the right relative to those characters already recorded. Thus, in the first cycle, as shown in FIGURE 4b, the characters a c c o 0 n are printed. After these characters have been printed the paper web is displaced by a distance W and, as shown in FIGURE 4c, the characters m and i are printed in the second cycle. FIGURE 40! shows the characters printed in the third cycle with a total displacement X. FIGURES 4e and 4 show the printing of characters with total displacements y and z respectively. After the fifth cycle the complete word has been printed and it will be seen that the spacing between the individual characters has been much improved. In order to show more clearly the relative displacements of the characters, FIGURES 4b through 1 have assumed that each displacement is in the same direction to the same extent, but it is to be understood that, as previously noted, in order to avoid a single large restoration movement of the web at the end of the fifth cycle, the individual increments of total displacement may be varied from the order shown in these figures.

It will be seen, therefore, that the location of the printed character'in a line is determined not only by the columnar printing positionat which it is printed but also by the printing cycle in which printing is effected. Therefore, the centre-to-centre distance of two characters which are printed at adjacent columnar printing positions is determined by the printing cycles in which each of the two characters are printed. For example, assume the displacement of the paper web results in a shift from left to right of the position on the web in which a character is printed in successive printing cycles. Then, if the left hand character of two characters printed at adjacent columnar printing positions is printed in a later printing cycle than the right hand character, the centre-to-centre distance of these two characters is less than the spacing of adjacent columnar printing positions. If the left hand character is printed in an earlier cycle than the right hand character, the centre-to-centre distance is greater than the spacing of adjacent columnar printing positions.

The lines of characters to be printed are entered into the stores 24 of the control circuits 23 from a computer 42. This computer operates under the control of a suitable programme to determine the location which each character is to occupy on the paper web. The centre-to-centre spacing of adjacent characters may be varied in depend ence upon the width of each of the characters in which case the computer calculates the position of each character in dependence upon the space required for the characters. For this purpose each character, when being processed by the computer, may be tagged with an indication of its width or a look-up table may be provided with information on character width. If desired the programme may control the computer such that the complete line of characters is justified, i.e. each line to be printed is arranged to have a predetermined uniform length.

The invention has been described in relation to a printing apparatus constructed to provide five displacement steps of the paper web but it may be constructed to provide any desired number of steps. While the foregoing description has dealt with the case where the paper web is displaced, it will be realised that the variable spacing of characters in a printed line is achieved by the production of successive steps of relative displacement between the recording medium and the nominal character printing positions determined in the present example by the position of the several character fonts arranged round the barrel. Thus, the same result may be achieved by moving the print barrel and its associated hammers while the paper web remains in a constant lateral position.

The same effect may be achieved in other kinds of printer. For example in a socalled chain printer the positions of characters within a line is determined by the timed operation of hammers in a printing cycle in which a font or fonts of type is moved in a direction parallel to the line of characters to be recorded. In this case the characters of the font are presented in turn to each character recording position nominally represented by the position of a hammer. Thus, movement of the paper web or movement of the hammers will also displace the actual character recording position in much the same way as hereinbefore described. In the case of the chain printer, however, yet a further method for displacing the character recording positions may be practised. Because the characters of the font are moving in the direction of the line to be printed, provided that the hammer faces are sufficiently large to cover the characters in a displaced position, it will be realised that by altering the timing of the hammers relative to the movement of characters along the line, the actual printed character on the recording medium will be laterally displaced. For example, if the characters in the font are moving from left to right across the paper, then, by arranging that a hammer is timed to operate slightly earlier than normal, a character printed by that hammer will be displaced slightly leftwards of the normal position. Hence, by progressively modifying the timing of the print hammers in a succession of printing cycles and allocating only certain characters to be printed in each cycle the proportional spacing of characters printed in the line may be varied in the manner shown in FIGURES 4b through 4 I claim:

1. Apparatus for printing a line of characters on a record medium including record medium supporting means; a plurality of fonts of characters, the characters of a font being of differing widths; means for supporting each font of characters, the supporting means being operable during a printing cycle to present in succession the characters of each font respectively at a separate predetermined columnar character printing position, a corresponding plurality of columnar character printing positions to said plurality of fonts respectively being equally spaced along the supporting means in the direction of the line by distances greater than the width of the widest character of the fonts; means for operating the supporting means during a succession of printing cycles to present characters of the different fonts concurrently at said columnar printing positions, control means for selecting characters to be printed in the line, the number of characters selected being no greater than said plurality of printing positions, and for allocating a printing cycle for the printing of each selected character; means responsive to said control means for printing in each cycle characters allocated to that cycle; and position modifying means operable between successive printing cycles to produce a relative displacement in the direction of the printing line between the printing positions and the record medium, the extent of the relative displacement being a fraction of the spacing between adjacent columnar character printing positions in the line.

2. Apparatus as claimed in claim 1, in which the control means includes first means for storing representations of characters to be printed in the line and further storage means operative to store signals indicating the printing cycles to which the respective stored characters are allocated.

3. Apparatus as claimed in claim 1 in which the displacement means is operative to displace the record medium relative to the columnar character printing positions.

4. Apparatus as claimed in claim 3 in Which the type characters are carried on a cylindrical type barrel, a separate font of type characters being provided for each columnar printing position.

5. Apparatus as claimed in claim 3 in which said displacement means includes selectively operable means to feed the record medium in a line spacing direction.

References Cited UNITED STATES PATENTS Higonnet et a1 197-843 Higonnet et a1 197-84.1 Demer et al.

Davis et a1.

Wright 197-133 Thiemann.

Potter 101-93 Hubbard 197-133 X West et al. 101-93 Greenwood 197-841 Walker 101-93 Wasserman 101-93 Christofif et al 101-93 WILLIAM B. PENN, Primary Examiner.

Us. 01. X.R. 

